As a conductive noise filter that is a conventional leakage current reducing apparatus, for example, a conductive noise filter is disclosed that is applicable to a system having a rectifier which converts the output of an AC power supply to DC voltage and a power converter for converting the DC voltage to AC voltage by switching operation of a semiconductor device for power, the conductive noise filter including: a common mode voltage detection circuit which is provided between the ground and a neutral point of ground capacitors connected in a Y-connection fashion to three-phase lines between the AC power supply and the rectifier, and detects common mode voltage occurring upon switching operation of the semiconductor device for power; an operational amplifier which amplifies the detected common mode voltage; and a cancelling voltage source which generates cancelling voltage having the same level as the common mode voltage and having an opposite polarity thereto, and superimposes the cancelling voltage onto the lines between the AC power supply and a connection point of the ground capacitors, thereby cancelling the common mode voltage (for example, see Patent Document 1).